Defect-Related Physical-Profile-Based X-Ray and Neutron Line Profile Analysis

Diffraction line broadening is caused by different defects present in crystalline materials: (1) small coherent domains, (2) dislocations, (3) other types of microstrains, (4) twin boundaries, (5) stacking faults, (6) chemical inhomogeneities, and (7) grain-to-grain second-order internal stresses. Line profile analysis provides qualitative and quantitative information about defect types and densities, respectively. Line profiles can broaden, be asymmetric, and be shifted, and these features can be anisotropic in terms of hkl indices. A few thumb rules help qualitative selection of lattice defect types. If the breadths do not increase globally with hkl, the defects are of size type, i.e., either the domain size is small or twinning or faulting, or both, is present. Whenever the breadths increase globally, the defects produce microstrains. Physically based profile functions can be determined for the different defect types and hkl anisotropy. The qualitative input about defect types based on different experimental observations allows adequate quantitative evaluation of the densities of different defect types by using physically modeled profile functions.